I don't think it's about the surface politeness factor, but about what kind of discussion is conducted. The ideal for an intellectual discourse is to have ques

I don't think it's about the surface politeness factor, but about what kind of discussion is conducted. The ideal for an intellectual discourse is to have questions be responded to with more questions. If question is met with answer, then old ground was covered, there was nothing new to see. If answer is met with answer, you're just ramming into each other. (And yes, there are disingenuous questions, but those tend to be "Jeopardy answers".) Politeness/rudeness does factor into that in that it "bulks up" the rhetoric. You can be a polite bullshitter or an insulting truth-seeker. You can use rhetoric tactically to goad the other person into the questioning mode, or you can use it to shut down the discussion.